Conventionally, in a microfabrication process for manufacturing a semiconductor device, a liquid crystal display device and the like, a reactive ion etching (RIE) apparatus is used. In the RIE apparatus, the inside of a chamber is first adjusted to enter a low pressure state, fluorine-based gas or chlorine-based gas is then introduced into the chamber to generate a plasma phase, and etching is performed. Since a member constituting the inner walls and inner portions of the RIE apparatus is susceptible to plasma and thus is likely to easily corrode when it is exposed to plasma, the member is usually coated with a protective film made of a material having a high plasma resistance such as yttria or alumina.
However, although the protective film such as yttria is coated onto the member constituting the inner walls and inner portions of the RIE apparatus, the protective film is still likely to degrade due to shedding of particles of the protective film, crack in the protective film and the like.